There is a tracker at http://twitter.com/IPv4Countdown which currently calculates that all of IPv4 address space will be allocated by the end of February 2011. The 100,000,000 address mark was broken on Sunday.
Prediction: A couple of years from now, we will scoff at this campaign sort of like we now scoff at the Y2K panic back in 1999, except this time, there's quite a lot less of alarmist coverage in the popular media.
Because, let's face it, this is not armageddon. "Allocated" does not mean "used". What we are seeing is a gold rush to stake out the last available unallocated pieces of IPv4 space. Or rather just a land grab, because it's unlikely that there is a lot of gold in them thar hills. But certainly, the operators who are now buying the remaining available pieces of IANA's unallocated address space are hoping to make some good money putting it up for sale or lease, or at least turn a profit. If the laws of demand and supply hold, and IPv6 doesn't suddenly take off spectacularly, IPv4 address prices can be expected to rise, and some actors are no doubt gambling that they will rise a lot.
A much more interesting question is how much of IPv4 space is really used up, not just allocated, but that is a lot harder to calculate, because there is no central authority like IANA where you can easily obtain numbers. Some of the big dinosaurs who were involved in the early stages of IPv4 development have huge pools of presumably mostly unused address space for which there is going to be a lot of demand eventually. Tracking the depletion of unallocated space is a good help for guessing when something will start to happen to the big Class A netblocks allocated to entities like General Electric (3/8, that is, all of 18.104.22.168 through 22.214.171.124; that's a rough 16 million IPv4 addresses), IBM (9/8), Xerox (13/8), Hewlett-Packard (15/7 — two consecutive Class A:s, 32 million addresses), Apple (17/8), MIT (18/8), and Ford Motor Company (19/8). The US Department of Defense also sits on several large blocks, and while they are presumably very reluctant to let go of this luxury, we can safely speculate that there is going to be a lot of pressure to transfer some of their addresses to civilian, even commercial use. But long before that, Ford will find a way to monetize their IPv4 asset, though perhaps not by going into direct competition with the likes of AT&T and Level 3 Networks.
A related question is under what terms you will be able to obtain an IP address in the future. Price is just one factor; and as the recent WikiLeaks incidents illustrate, obtaining an IP address which offers true freedom of expression might be even more important, for those who have something unpopular to say. And in an ironical twist, it seems that totalitarian states are going to be the only ones offering this scarce commodity, to everyone else except their own citizens. It seems that WikiLeaks is struggling to avoid moving their servers to the Wild East, because such freedom comes at a price, which is measured partly in ethical terms, but also partly in security; depending on what at least parts of the international community will refer to as a rogue state and its inevitable whims is hardly a viable long-term solution.
In the meantime, don't panic, but do keep on monitoring the situation. We are not trying to say that IPv4 address space depletion is not a problem, and we certainly are in favor of sustainable development, whether that means IPv6 or a reform of IPv4. But we would like to point out that this is just another phase of a chronic problem, not an acute crisis for IPv4.